In an long term evolution_(LTE) communications system and a long term evolution advanced (LTE-A) communications system, when user equipment_(UE) is not performing a service or is not receiving or sending data, the UE may generally be in an idle state. When the UE needs to set up a service, or to receive or send data, the UE needs to switch from an idle state to a connected state before receiving or sending data.
During random access, the UE selects a random access preamble and sends the random access preamble to an evolved NodeB (eNB), and the eNB allocates an uplink resource to the UE according to the random access preamble. The random access preamble can reflect only that a volume of data to be sent subsequently by the UE is greater than or less than a threshold, and when the data to be sent by the UE is greater than the threshold, the eNB cannot accurately obtain a volume of the data according to the received random access preamble that is sent by the UE. Therefore, the base station cannot allocate resources accurately, which easily results in wasting of resources, or uplink data is transmitted for multiple times, which not only wastes a scheduling command but also leads to a transmission delay.